Projector

ABSTRACT

A projector having optical components, a power source unit, and a light source unit. The projector is capable of lowering its internal temperature utilizing: a first, second, and third fan ( 41, 42, 43 ) provided near the optical components for introducing external air from outside the projector to cool the optical components; and a fourth, fifth, and sixth exhaust fan ( 16, 17, 18 ). The fourth fan ( 16 ) blows the air that was taken in by the first, second, and third fan ( 41, 42, 43 ) and has cooled the optical components, onto the light source unit to further cool the light source unit. The fifth and sixth exhaust fans ( 17, 18 ) discharge the air that has cooled the light source unit and power supply unit out of the projector.

FIELD OF THE INVENTION

This invention relates to a projector capable of properly lowering itsinternal temperature.

BACKGROUND OF THE INVENTION

With recent rapid development of projector technology, major marketinterest is directed to the research and development of ahigh-performance compact projector that is operable at a lowtemperature.

General purpose liquid crystal projectors available in the market havefour intake fans installed near the liquid crystal panels (hereinafterreferred to as LCPs), along with two exhaust fans each discharging anamount air three times as much as the intake air sucked in by eachintake fan. In such arrangement, it is difficult to design a liquidcrystal projector not affected by hot air lingering in the projector.

Therefore, there is a need in the market for a compact projector havinghigh-luminosity, equipped with a minimum number of fans, and yet havinga low fan noise level, and satisfactory temperature compatibility.

SUMMARY OF THE INVENTION

In view of the above-mentioned circumstances, the present invention isdirected to a liquid crystal projector capable of efficiently loweringthe temperature inside the projector that has optical components, apower unit, and a light source unit.

In accordance with one aspect of the invention, there is provided aprojector having: at least a light source unit; optical componentsadapted to decompose a beam of source light from the light source unitinto beams of three primary colors (red, green, and blue), modulate thethree colored beams based on an image signal received, compose the threemodulated beams into a beam of full-color imaging light, and project theimaging light; and a power supply unit for supplying electric power tothe light source unit and optical components, the projector comprising:

a first, second, and third fan (41-43) each provided near the opticalcomponents to introduce external air from outside the projector to coolthe optical components; and

a fourth, fifth, and sixth fan (16-18) for discharging internal air ofthe projector, with the fourth fan (16) adapted to cool the light sourceunit by blowing into the light source unit the air that has beenintroduced by the first, second, and third fan (41, 42, 43) and hascooled the optical components, and the fifth and sixth fans (17, 18)adapted to discharge out of the projector the air that has cooled thelight source unit and the power supply unit.

In this arrangement, the number of fans for cooling the opticalcomponents can be reduced to three, so that the total number of fansinstalled in the projector can be reduced to six. At the same time, airflows inside the projector are improved in that the temperatures of theoptical components near the respective LCPs and the casing of theprojector are lowered. Thus, this arrangement is advantageous for ahigh-performance projector.

The first through fourth fans can be centrifugal fans.

These fans can suck in external air and blow off the air topredetermined interior sections of the projector that must be cooled.

On the other hand, the fifth and sixth fans (17, 18) are preferablyaxial fans.

These fans can powerfully exhaust the projector.

Moreover, the first and third fans (41, 43) are preferably arranged onone side of the optical components for composing the three color imaginglight, while the second fan (42) is preferably arranged on the otherside of the optical components to face the first and third fans (41, 43)across the optical components.

This arrangement ensures efficient performance of the fans in theprojector.

The fifth and sixth fans (17, 18) are preferably arranged on one side ofthe projector and behind the light source. The fourth fan (16) ispreferably arranged near, and on the other side of, the light sourceunit to face the fifth and sixth fans (17, 18) across the light sourceunit.

This arrangement permits efficiently discharging, out of the projector,the air that is fanned by the fifth and sixth fans to the light sourceunit by the fourth fan (16) to cool the light source unit.

In this case, the amount of the air to be discharged by the fifth andsixth fans (17, 18) is preferably at least 3 times as much as the amountof the air taken in by the first, second, and third fans (41, 42, 43).

Thus, the air that is externally introduced into the projector to coolthe interior thereof can be efficiently discharged out of the projector.

Preferably, the fifth fan (17) primarily discharges the air that hascooled the light source unit, while the sixth fan (18) primarilydischarges the air that has cooled the power supply unit.

Thus, the internal air of the projector can be efficiently discharged.

Preferably, the fifth and sixth fans (17, 18) are obliquely aligned toeach other so that the air streams expired from these fans cross eachother.

This arrangement can mix the two streams of air into an air streamhaving a lower average temperature as they are discharged from theprojector.

The projector may be further provided, between the second fan (42) andthe fourth fan (16) and near the fourth fan (16), with a rectifyingplate (500) for guiding air flow.

Thus, although the second and fourth fans are separated from each otherat a short distance, they do not interfere with each other and performnormal operation, that is, the air expired from the second fan and hascooled predetermined sections of the projector is inspired by the fourthfan to cool the light source unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a projection type image displayapparatus in the form of a liquid crystal projector in accordance withone embodiment of the invention, as viewed from an upper obliqueposition with respect to the front end of the projector.

FIG. 2 is a perspective view of the liquid crystal projector as seenfrom an upper oblique position with respect to the rear end of theprojector.

FIG. 3 is a perspective view of the projector, with its upper covershown in FIG. 1 removed.

FIG. 4 is a perspective view of the projector, with its main controlboard removed.

FIG. 5 is a perspective view, with its optical system further removed.

FIG. 6 is a plan view of the arrangement of the components shown in FIG.5.

FIG. 7 shows in schematic diagram an arrangement of the optical systemof the projector.

FIG. 8 is an enlarged perspective view of a principal part of the lampcooling structure of the embodiment, as viewed from an upper obliqueposition with respect to the front end of the projector.

FIG. 9 is a perspective view of an air duct for use in the lamp coolingstructure of FIG. 8 with the upper half section thereof removed, asviewed from an upper oblique position with respect to the rear end ofthe air duct.

FIG. 10 is a perspective view of a light source unit shown in FIG. 9with the lamp stand thereof removed.

FIG. 11 is a longitudinal cross section of a principal part of the airduct.

FIG. 12 is an enlarged view of the main section of the opticalcomponents cooling structure in accordance with the embodiment, asviewed from an upper oblique position with respect to the front endthereof.

FIG. 13 is a plan view of the optical components cooling structure.

FIG. 14 is a plan view of the optical components cooling structure withthe optical components removed.

FIG. 15 is a rear elevation of the air duct with the lower half sectionthereof removed.

FIG. 16 is a perspective view showing an arrangement of the exhaust fanunit of an exhaust system in accordance with the embodiment.

FIG. 17 is an oblique perspective view of the exhaust fan unit shown inFIG. 16, as viewed from behind.

FIG. 18 shows in perspective view an overall arrangement of the fans forlowering the internal temperature of the projector, with arrows showingthe flows of the air taken in, and discharged from, the projector by thefans.

FIGS. 19-21 show an air rectifying structure for cooling an IC installedon a network card, using a fan (41).

FIGS. 22-24 show another rectifying structure for cooling the IC, usinga fan (42).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described in detail by way of example withreference to the accompanying drawings. FIG. 1 is a perspective view ofa projection type image display apparatus in the form of a liquidcrystal projector in accordance with one embodiment of the invention, asviewed from an upper oblique position with respect to the front end ofthe projector. FIG. 2 is a perspective view of the projector as viewedfrom an upper oblique position with respect to the rear end of theprojector. FIG. 3 is a perspective view of the projector with its uppercover shown in FIG. 1 removed. FIG. 4 is a perspective view with itsmain control board removed. FIG. 5 is a perspective view with theoptical components removed. FIG. 6 is a plan view of the componentsshown in FIG. 5.

Referring to FIGS. 1 and 2, there is shown a liquid crystal projector 1,having a case 2 serving as the frame thereof. The case is generally anoblong small thin parallelepiped having a width larger than the length.The case is has an upper cover 2 a and a lower box 2 b. The interior ofthe projector can be seen when the upper cover 2 a and a main controlboard 4 are removed, as seen in FIG. 4.

It is seen in FIG. 4 that there is provided in the left front end of theprojector a projector window 5 accommodating therein a projection lens4. Formed in the left front section of the upper cover 2 is amanipulation window 6 in association with the projector window 5. Afocus adjuster 4 a for adjusting the projection lens 4 can be seen inthe window 6. Installed on the left rear section of the upper cover 2 aare operation buttons and indicators 7.

In accordance with another embodiment of the invention, there is formeda lattice of a multiplicity of narrow-spaced air outlet holes 8 in theright sidewall of the lower box 2 b, as shown in FIG. 2. Provided at theopposite front corners of the bottom of the lower box 2 b are legs 9 foradjusting the heights of the corners. Provided on the rear wall of thelower box 2 b are a power supply terminal 10 to be connected to a powersupply plug and an input-output power supply terminal 11 connected to amulti-voltage power supply cable.

As shown in FIGS. 3 and 4, a light source unit 12 is installed in theright end section of the case 2. The light source unit 12 and an opticalsystem 13 associated with the projection lens 4 are arranged in anL-shape configuration. Arrange in front of the light source unit 12 is apower supply unit 14. The power supply unit 14 includes: a power circuitboard having thereon an electric circuit for supplying electric power todifferent parts of the projector; a dedicated ballast circuit board forsupplying electric power to the lamp; and a noise suppression filter 15for suppressing the noise entering the power supply terminal 10.

In the embodiment shown herein, the noise suppression filter 15 isseparated from the power supply unit 14, and is installed as close tothe rear wall of the case and to the power supply unit 14 as possible.More particularly, the power supply unit 14 is arranged along the frontwall of the oblong case 2, and the noise suppression filter 15 thatincludes an iron core coil 15 a is arranged directly behind the powersupply unit 14 and on an upper section of the rear wall of the powersupply board.

In accordance with a further embodiment of the invention, a centrifugalfan 16 (fourth fan) serving as an intake fan for cooling the lamp isarranged behind the light source unit (i.e. on the rear side of thelight source unit). Provided on one side of the light source unit 12 isan axial exhaust fan serving as a lamp cooling fan (fifth fan) 17. Inaddition, another axial fan serving as a further exhaust fan (sixth fan)18 for discharging internal air is provided on one side of the powersupply unit 14 and in parallel with the fan 17.

Referring to FIG. 7, there is shown an arrangement of the optical system13 of the invention. It should be understood, however, that theinvention is not limited to the optical system shown in FIG. 7. Rather,the invention can be applied to various other types of optical systems.

As seen in FIG. 7, white light emitted from the lamp 19 of the lightsource unit 12 is passed to a first dichroic mirror 25 via a condenserlens 20, first integration lens 21, second integration lens 22,polarization beam splitter (PBS) 23, and condenser lens 24.

Each of the first integration lens 21 and the second integration lens 22consists of a rectangular array of many fly-eye lenses, and has afunction to uniformize illumination intensity of the white light comingfrom the lamp 19.

The polarization beam splitter (PBS) 23 has a polarization splittingfilm and a retardation plate (or a half-wave plate). The polarizationsplitting film allows P-polarization component of light that has passedthrough the second condenser lens 22 to pass through the film, butcauses S-polarization component to slightly change its optical path asit passes through the film. The P-polarization component that has passedthrough the polarization splitting film is converted into S-polarizationcomponent by the retardation film placed at the light-exiting side ofthe PBS 23, so that substantially all the light entering the beamsplitting film will become S-polarized as it passes through theretardation film.

The light that has passed through the PBS 23 is passed to the firstdichroic mirror 25 via the condenser lens 24. The first dichroic mirror25 reflects the blue component of light, but allows red and greencomponents to pass through it, so that the red and green componentsreach a second dichroic mirror 26. The second dichroic mirror 26reflects the green component of light, and allows the red component topass through it. As a result, white light from the lamp 19 is split bythe first and second dichroic mirrors 25 and 26, respectively, intothree beams of blue, green and red light.

The blue light reflected by the first dichroic mirror 25 is thenreflected by a total reflection mirror 27. The green light reflected bythe second dichroic mirror 26 is led to an image forming optical system32. The red light that has passed through the second dichroic mirror 26passes through relay lenses 28 and 30 and is reflected by further totalreflective mirrors 29 and 31 and led to the image forming optical system32.

In the image forming optical system 32, prism components 35 such asseparate LCPs 34 r, 34 g, and 34 b for red, green, and blue light(respectively referred to as R-, G-, and B-LCP) are detachably mountedon the three sides of a cubic color composition prism 33 as shown inFIG. 4. Further, a polarization plate 36 r (referred to as exit sidepolarization plate) for red light is provided between the colorcomposition prism 33 and the R-LCP 34 r.

Similarly, an exit side polarization plate 36 g and a pre-stagepolarization plate 37 g for green light are provided between the colorcomposition prism 33 and the G-LCP 34 g, and an exit side polarizationplate 36 b and a pre-stage polarization plate 37 b for blue light areprovided between the color composition prism 33 and the B-LCP 34 b.Further polarization plates 38 r, 38 g, and 38 b (respectively referredto as incidence side polarization plates) and condenser lenses 39 r, 39g, and 39 b for red, green, and blue light (respectively referred to asR-, G-, and B-condenser lens) are arranged on the respective incidencesides of the R-, G-, and B-LCPs 34 r, 34 g, and 34 b.

As a consequence, the blue light reflected by the first dichroic mirror25 and the total reflection mirror 27 is led to the B-condenser lens 39b and further to the color composition prism 33 via the incidence sidepolarization plate 38 b, B-LCP 34 b, pre-stage polarizing plate 37 b,and exit polarizing plate 36 b. The green light reflected by the seconddichroic mirror 26 is led to the G-condenser lens 39 g and further tothe color composition prism 33 via the incidence side polarization plate38 g, G-LCP 34 g, pre-stage polarizing plate 37 g, and exit sidepolarization plate 36 g. Similarly, the red light that has passedthrough the first and second dichroic mirrors 25 and 26, respectively,and is reflected by the two total reflective mirrors 29 and 31, is ledto the R-condenser lens 39 r and further to the color composition prism33 via the incidence side polarization plate 38 r, R-LCP 34 r, and exitpolarizing plate 36 r.

The three colored beams of imaging light introduced into the colorcomposition prism 33 are composed to a colored imaging light beam, whichis projected by the projection lens 4 onto a front screen.

Referring to FIGS. 8-11, there is shown in enlarged perspective or planview an arrangement of a main section of the lamp cooling structure.More particularly, FIG. 8 shows the cooling structure as viewed from anupper oblique position with respect to the front end of the coolingstructure; FIG. 9 shows the cooling structure as viewed from an upperoblique position with respect to the rear end, the figure depicting thecondition of the duct of the cooling structure with the upper sectionthereof removed; FIG. 10 shows the cooling structure with the lamp standthereof removed; and FIG. 11 is a cross section of a main section of thecooling structure as viewed from behind.

In the embodiment shown herein, the lamp 19 has an arc tube 191, whichis a high-pressure mercury tube or a halogen tube; a parabolic reflectorconfigured to cover the arc tube 191; and a light-reflective cover 192having a front opening. The light-reflective cover 192 is provided withan air inlet 193 formed at the edge of the front opening thereof and anair outlet 194 facing the air inlet 193, as shown in FIG. 10.

This lamp 19 is installed on an aluminum lamp stand 195 as shown inFIGS. 8 and 9. The aluminum lamp stand 195 is equipped with aheat-resistive glass plate 196 for covering the front opening of thelight-reflective cover 192, and with a ventilation net 197 having amultiplicity of holes in association with the air inlet 193 and airoutlet 194 such that the net will prevent debris of the arc tube 191from being scattered in the event that the arc tube 191 is fractured.

Conventional lamp cooling structures are so designed to cool only thelamp using fans and exhaust ports that the temperature of the exhaustedair is high as it is discharged from the exhaust ports. Such prior artarrangement is not suitable for a projection-type compact high-powerimage display apparatus such as a liquid crystal projector, since thetemperature of the exhausted air would become excessively hot after theair had cooled a high-power lamp. In other words, it is difficult withthe conventional cooling structure to lower the temperature of theexhaust air and cool the lamp simultaneously. One way to lower theexhaust air temperature is to increase the output power (rotationalspeed) of the fan, which, however, increases fan noise.

In the embodiment shown herein, therefore, there are provided a lampcooling system that includes:

an air outlet 161 associated with an air inlet 193 formed in thelight-reflective cover 192 to ventilate the lamp 19;

an intake fan 16 (fourth fan) sending air to exterior-cooling airoutlets 162 and 163 formed to face the light-reflective cover 192; and

an exhaust fan 17 (fifth fan) for discharging the ambient air around thelamp 19 through the air outlet holes 8 formed in one sidewall of thecase 2. The intake fan 16 is a centrifugal fan, while the exhaust fan 17is an axial fan.

It is noted that the exterior-cooling air outlets 162 and 163 associatedwith the intake fan 16 are arranged away from the external centralsurface of the light-reflective cover 192 of the lamp 19. It is alsonoted that the exhaust fan 17 is obliquely placed. That is, it isarranged to inspire air towards the exterior-cooling air outlets 162 and163 associated with the intake fan 16.

A duct 164 extends from the intake fan 16 to one side of the lamp 19posterior to the intake fan 16. The air outlets 161, 162, and 163 areformed at the end of the duct 164 facing the lamp 19. Theinterior-cooling air outlet 161 is formed in association with the airinlet 193 formed in the light-reflective cover 192 of the lamp 19. Thetwo exterior-cooling air outlets 162 and 163 are formed above and belowthe central region of the exterior of the light-reflective cover 192.

As described above, the distance from the central region of the exteriorof the lamp 19 to the exterior-cooling air outlets 162 and 163 and theoblique angle of the direction of inspiration of the exhaust fan 17relative to the exterior-cooling air outlets 162 and 163 are set basedon the cooling requirement of the lamp 19 and the permissible exhaustair temperature.

In this arrangement, although the lamp 19 has the arc tube 191 that canbe heated to a very high temperature, the interior of the lamp 19 can beefficiently cooled owing to the interior-cooling air outlet 161 of theintake fan 16. The exterior of the light-reflective cover 192 of thelamp 19 (including a neck section that protrudes from the rear end ofthe cover 192) will not be heated as high as the interior of the lamp19, and is cooled to a moderate temperature by the intake fan 16 sendingair through the exterior-cooling air outlets 162 and 163, though theintake fan 16 is located away from the central region of the coverexterior.

It is noted that the exhaust fan 17 is arranged with its air inspirationface obliquely oriented to the exterior-cooling air outlets 162 and 163associated with the intake fan 16 adjacent the lamp 19, so that the airis discharged from the exterior-cooling air outlets 162 and 163 to theexterior of the lamp to cool it, and, at the same time, partly taken inthe exhaust fan 17 to be mixed with the hot air that discharged from thelamp 19, thereby lowering the temperature of the exhaust air from theexhaust fan 17.

As a result, reduction in temperature of both the lamp 19 and theexhaust air, and also reduction of the fan noise, can be simultaneouslyachieved without increasing the output power of the intake fan 16(fourth fan) and exhaust fan 17 (fifth fan).

It should be noted that the two exterior-cooling air outlets 162 and 163associated with intake fan 16 located at a distance from the centralregion of the exterior of the lamp 19 can cool the exterior of the lamp19 substantially uniformly.

As described above, the distance from the central region of the exteriorof the lamp 19 to the exterior-cooling air outlets 162 and 163associated with the intake fan 16 and the oblique angle of the airinspiration face of the external fan 17 with respect to the outlets canbe set based on the cooling requirements of the lamp 19 and theallowable temperature of the exhaust air. This configuration enablessimultaneous realization of downsizing and power up of the lamp 19.

It is further noted that the intake fan 16 may have a large positionalfreedom, since the air outlets 161, 162, and 163 associated with theintake fan 16 are formed in the wall of the duct 164 that extends fromthe intake fan 16 to the lamp 19.

Thus, in the liquid crystal projector 1 in accordance with theembodiment shown herein, cooling of the lamp 19, lowering of thetemperature of the exhaust air, and reduction of fan noise can besimultaneously achieved without increasing the output powers of the fans16 and 17 by the lamp cooling structure.

Referring to FIGS. 12-15, there is shown in enlarged view a majorsection of the optical component cooling structure. More particularly,FIG. 12 is a perspective view of the structure as viewed from an upperoblique position with respect to the front end thereof; FIG. 13 is aplan view of the structure; FIG. 14 is a plan view with the opticalcomponents including LCPs removed; and FIG. 15 is a rear elevation ofthe structure with the lower half section of the duct removed.

As is well known, there are provided in conventional projectors threecooling fans one for each of the R-, G-, and B-LCPs and associatedpolarization plates placed on the incidence and exit sides of therespective LCPs.

However, a temperature rise in, and hence the required cooling for, eachof the R-, G-, and B-LCPs and associated polarization plates disposed onthe incidence and exit sides of the respective LCPs varies from one LCPto another, depending on the degree of ultraviolet [UV] deterioration.Particularly, in order to prevent deterioration, the B-LCP and itsassociated polarization plates require more cooling than other panelsand plates, since blue light lies close to the ultraviolet zone.

Conventionally, enhancement of lamp output, down-sizing, and cost savingof a projection type image display apparatus such as a liquid crystalprojector have been simultaneously pursued through improvement of lampluminosity and luminosity per unit area.

However, prior art cooling systems utilizing a fan for each of the colorLCPs cannot deal with the cooling of a projector having an enhanced lampluminosity and luminosity per unit area. If, as a countermeasure, theoutput powers (rotational speeds) of the fans are increased, fans noisewill increase to an unacceptable level. In addition, the PBS must becooled.

In the present invention, therefore, there are provided six air outletsr1, r2, g1, g2, b1, and b2, provided at the incidence sides as well asexit sides of the respective LCPs 34 r through 34 b, to discharge airsent by the first through third intake fans 41-43 via respective firstthrough third air ducts (the ducts hereinafter referred to as air ducts)411-431. There is also provided an air outlet p1 for sending onto thePBS 23 air sent by the air intake fan 43 via the third air duct 431. Inaddition, a further air duct is connected from the fan 41 to each of theincidence side and exit side outlets b1 and b2, respectively, for theB-LCP 34 b to separately deliver additional cooling air from the intakefan 41. The intake fans 41-43 (first through third fans) are centrifugalfans.

In other words, the fans and the air ducts can be configured as follows.

The intake fan 43 sends air to the incidence side outlet b1 associatedwith the B-LCP 34 b and to the outlet p1 for the PBS 23, and the twoother intake fans 41 and 42 send air to the incidence side outlets r1and g1 and to the exit side outlets r2 and g2 associated with therespective R-LCP 34 r and G-LCP 34 g.

More particularly, the air ducts of the embodiment are configured asfollow. One of the two intake fans, intake fan 42 for example, sends airvia a second air duct 421 to the incidence side and exit side outlets g1and g2, respectively, for the G-LCP 34 g, while the other intake fan 41sends air via an extended first air duct 411 to the incidence side andexit side outlets r1 and r2, respectively, for the R-LCP 34 r and to theexit side outlet b2 for the B-LCP 34 b.

In this arrangement, the three intake fans 41-43 can cool the incidencesides and the exit sides of the respective LCPs 34 r, 34 g, and 34 b aswell as the PBS 23. Furthermore, the incidence side and the exist sideof the B-LCP requiring a larger amount of cooling air can besufficiently cooled by the separate intake fans 43 and 41. Thus, evenwhen the luminosity and luminosity per unit area are increased, the LCPs34 r, 34 g, and 34 b, and the polarizing plates 36 r, 36 g, 36 b, 37 g,37 b, 38 r, 38 g, and 38 b as well as PBS 23 can be cooled by the firstthrough third intake fans 41-43 without increasing the output powers(rotational speeds) of these fans, and hence without increasing fannoise either.

Alternatively, the ducts can be arranged in the following manner. Theintake fan 43, say, sends air to the incidence side outlet b1 for theB-LCP 34 b and to the outlet p1 for the PBS 23, while other two intakefans 41 and 42 send air to the respective incidence side outlets r1 andg1 and to the exit side outlets r2 and g2 for the R-LCP 34 r and G-LCP34 g, respectively, and to the exit side outlet b2 for the B-LCP 34 b.

Accordingly, the function and merits of the optical component coolingstructure as described above can be achieved utilizing the shortest airduct in the optical system 13 if the B-LCP 34 b is arranged adjacent thePBS 23 in accordance with the embodiment shown herein. It is noted thatthe air sent from the intake fan 41 to the R-LCP 34 r generating theleast heat is bifurcated to the exit side outlet b2 for the B-LCP 34 b,and to the G-LCP 34 g generating the most heat if the air sent from theintake fan 42 thereto is insufficient.

The ducts can be alternatively arranged as follows. One of the intakefans 41 and 42 (fan 42 for example) may be adapted to send air to theincidence side and the exit side outlets g1 and g2, respectively, forthe G-LCP 34 g, while the other fan (fan 41 for example) may send air tothe incidence side and exit side outlets outlet r1 and r2, respectively,for the R-LCP 34 r and to the exit side outlet b2 for the B-LCP 34 b.This arrangement enables realization of the function and the merits ofthe optical component cooling structure as described above withoutcomplicating duct structure.

Since the liquid crystal projector 1 in accordance with the embodimentof the invention has an optical component cooling structure as describedabove, three fans can cool the LCPs, polarization plates, and PBSwithout raising the output power (or rotational speed) of the fans orwithout raising the fan noise, even if the luminosity of the lamp andluminosity per unit area are raised.

Next, the power supply unit of the embodiment will now be described. Ingeneral, a noise suppression filter is provided on the electric circuitboard of a power supply unit, as stated above.

A need exists for a compact and cost effective projection type imagedisplay apparatus such as a liquid crystal projector equipped with alamp having an enhanced output power to provide high luminosity, forwhich the output power of the power supply unit must be enhancedaccordingly.

In a low-power model, there is no problem in mounting a noisesuppression filter on the electric circuit board, as in conventionalprojectors. However, in a high-power model, a noise suppression filterhas an iron core that cannot be down-sized, and hence the power supplyunit must become large.

As the power supply unit becomes large, a larger fan must be used tocool the unit, or the output (or rotational speed) of the fan must beraised, which results in degradation of the cooling capability of theprojector and increase fan noise. If, as a measure, an independent noisesuppression filter is separately installed, its connecting cord islikely to generate a noise. In addition, EMC (electromagneticcompatibility) of the filter is difficult to secure, since it containsan additional iron core. It also adds an extra cost to the projector.

In the present embodiment, therefore, the noise suppression filter 15 isseparated from the power supply unit 14 and placed as close to the rearwall of the projector having a power supply terminal 10 and to the powersupply unit 14 as possible, as described in the above example.

More particularly, when the power supply unit 14 is arranged adjacentthe front wall of the oblong case 2, the noise suppression filter 15 isarranged along the opposite rear wall of the case 2 (i.e., opposite thepower supply unit 14).

In this arrangement, even if the output of the lamp 19 is raised, thepower supply unit 14 can be down-sized. Hence, the cooling performanceof the fan can be improved and fan noise can be reduced. Further, byminimizing the length of the connecting cord, not only the EMC isimproved (since the amount of the iron core used is reduced) but alsothe cost of the projector is reduced accordingly.

Since the noise suppression filter 15 is arranged adjacent the rear wallof the case 2 that has the power supply terminal 10, it requires nopower cord that hinders use of the sidewall of the case 2, therebyconveniently providing the function and merits as described above.

Alternatively, the power supply unit 14 can be arranged along the frontwall of the oblong case 2 and the noise suppression filter 15 arrangedon the opposite rear wall (i.e., opposite the power supply unit 14) tominimize the length of the connection cord. Then, the same function andmerits as described above can be achieved without complicating thearrangement of the components in the case 2.

As described above, even if the output power of the lamp 19 is enhanced,the cooling capability, fan noise level, and the EMC of the projector 1are all improved in accordance with the embodiment shown, therebyenabling realization of a cost effective liquid crystal projector.

In the example shown herein, the case 2 is oblong, i.e. the width islarger than the length, so that the connection cord can be minimized inlength by arranging the power supply unit 14 and noise suppressionfilter 15 in parallel with each other on the front wall and rear wall,respectively. In the case where the case 2 is longer than is wide,however, the cord cannot be minimized as stated above. In this case, thenoise suppression filter may be arranged to extend in the longitudinaldirection and near the rear wall and the power supply unit.

Next, the exhaust structure in accordance with the present embodimentwill now be described. Conventionally, two exhaust fans for cooling thelamp and power supply unit are arranged in a row along the lamp.

As described above, enhancement of the output power of the lamp anddown-sizing of a projector are overwhelmingly needed for a projectiontype image display apparatus such as a liquid crystal projector. Infulfilling these objects simultaneously, it is an essential issue tolower the temperature of the exhaust air and fan noise, since the lampwill generate hot air.

However, in the conventional technology, in order to lower the fan noisearranged in a row, they must be a disposed at a distance from thesidewall of the case to thereby leave a space between the fans and thesidewall. This arrangement, however, prevents down-sizing of theprojector. Furthermore, in order to mix hot air expelled from the hotlamp with rather cooler air discharged from the power supply unit, thesefans are lined up at an angle, i.e. obliquely arranged in a V-shapeconfiguration, which arrangement also disadvantageously requires somespace for the fans, which is not favorable to the down-sizing.

In the present embodiment, therefore, the fan 17 (fifth fan) forprimarily discharging air from the lamp 19 (installed in the lightsource unit 12) and the exhaust fan 18 (sixth fan) for primarilydischarging air from the power supply unit 14 are arranged side by side,as shown in FIGS. 3 and 4, in such a way that one end of the exhaust fan17 (fifth fan) is skewed inwardly (i.e. one end offset inward of thecase) and that one end of the exhaust fan 18 (sixth fan) is offsetinside the expiration face of the skewed fan 17 so as to cause the airstream expired from the exhaust fan 17 (fifth fan) is directed to theair stream expired from the exhaust fan 18 (sixth fan).

In addition, the exhaust fan 17 is angled (i.e. placed at an angle) to alatticed or narrow-spaced many exhaust holes 8 formed in the sidewall ofthe case, so that the air stream from the holes 8 are discharged in anoblique forward direction.

As shown in FIGS. 16 and 17, in implementing the above-described fansystem, the exhaust fans 17 and 18 may be preliminarily fixed to theframe to unitize them with the frame 50 of the case 2. If an exhaust fanunit 51 thus formed is provided at a predetermined position below thelower box 2 b of the case 2, the above described arrangement structurecan be easily obtained.

It is noted that, since the exhaust fan 17 inspires hot air collectedfrom the lamp 19, the central section of the fan 17 behind the motor iscovered with a panel 52 for protecting the motor against the hot air, asshown in FIG. 17.

In this fan configuration, the exhaust fan 17 is inwardly skewed (orobliquely angled to the wall of the case), so that the fan does notprevent down-sizing of the projector. Further, this configurationpermits a gap to be created between the sidewall of the case and theexhaust fan 17, thereby facilitating reduction of the fan noise.Moreover, temperature of the exhaust air can be reduced due to the factthat hot air from the lamp 19 is mixed with relatively cooler air fromthe power supply unit 14 before they are discharged from the projector.Although the lamp gets heated to a high temperature, the above describedeffects can be achieved much easier in this arrangement than inconventional one owing to the space between the lamp and the exhaustfan.

It should be understood that the power supply unit 14 is not so high asthe lamp 19, so that the air sent to the power supply unit 14 can bealso used to ventilate the lamp 19, though the exhaust fan 18 isprimarily used to ventilate the power supply unit 14.

It is noted that, since the exhaust fan 17 (fifth fan) for exhaustingthe lamp 19 is arranged at an angle to the many latticed narrow-spacedexhaust holes 8 formed in the sidewall of the case, the hot exhaust airfrom the lamp 19 does not readily flow through it, so that the air canbe easily mixed with the relatively cooler air expired from the exhaustfan 18 (sixth fan).

Furthermore, since the hot air discharged from the lamp 19 is releasedfrom the skewed fan 17 in an oblique or sideway direction through theholes 8, the hot air is prevented from being discharged to the operatorworking on the projector.

Thus, a down-sized, low-noise, well ventilated liquid crystal projector1 (discharging only low-temperature exhaust air) can be realized byimplementing the exhaust fans 17 an 18 in exhaust fan configuration inaccordance with the embodiment shown.

Further, if there is an unused space inside the case 2 available for thefan 18 after the exhaust fan 17 is obliquely arranged as describedabove, then the exhaust fan 18 may be also angled in the oppositedirection as compared to the fan 17 to maximize mixing of the exhaustair from the two fans.

Next, a method of cooling the network card (or LAN card or LAN board) ofthe projector will now be described. FIGS. 19-21 illustrate an airrectifying structure for use in cooling an integrated circuit (IC)installed on a network card by the fan 41 (first fan). FIGS. 22-24illustrate another rectifying structure for cooling the IC installed onthe network card using a fan 42 (second fan).

A new type of projector can be equipped with a wireless or wired networkcard (LAN card) 800 as shown in FIG. 20. The card allows fast datatransfer to and from an external network. The network card 800(especially the integrated circuit in the network card) in operationgenerates heat that must be effectively removed. If not removed,thermorunaway of the network card will incur failure of the network carditself, and hence the projector. Therefore, this thermorunaway problemmust be solved.

One way to cool the network card 800 is to re-distribute the volume ofthe air sent by the fans 41 and 42 to the optical components mounted onthe prism such that the optical components as well as the network cardare properly cooled. Specifically, it is desirable that the followingitems are included in this cooling scheme.

As an optimal scheme, the air sent by the fan 41 may be bifurcated tothe optical components for blue light (hereinafter referred to asB-optical components) and optical components for red light (hereinafterreferred to as R-optical components). To do this, a branching air duct412 may be connected to the first air duct 411 delivering air to theR-optical components so as to deliver part of the air to the networkcard 800, thereby appropriately cooling the IC operating at acomparatively high temperature on the network card 800.

Alternatively, a branching air duct 422 for sending air from the fan 42to the network card 800 may be connected to the second air duct 421sending air to the optical components for green light (hereinafterreferred to as G-optical components), thereby appropriately cooling the.

In this way, using such a cooling scheme as described above, the networkcard 800 can comply with the thermal requirement without using heatdissipative rubber on the network card 800.

In what follows an exemplary overall arrangement of the cooling ductswill be described in detail. In the case of a high-power compactprojector (having for example 0.63-inch LCPs and luminosity of 3000lumens) as shown in FIG. 15, operating temperatures of the respectiveoptical components are comparatively high, so that it is necessary toprovide them with effective cooling. Of the optical components near theprism, the R-optical components can be cooled easier than the G-opticalcomponents, while cooling of the B-optical components is most difficult.In order to fulfill required cooling conditions, it is thereforenecessary to design proper cooling air ducts for deliveringappropriately controlled amount of air to the R-, G-, and B-colorcomponents by the three fans.

Since the R-optical components are easiest to cool, the first air duct411 is preferably configured to deliver the air sent from the fan 41 notonly to the R-optical components but also to the R-polarization plateand the B-optical components. The fan 42 is used to cool only theG-polarization plate. The fan 43 collaborates with the fan 41 to coolthe B-optical components. The air delivered to the B-optical componentsis preferably bifurcated to the PBS 23. The configuration of the ductsthat provides the most optimal air distribution for cooling all of thethree color optical components has been found through experimentsconducted by the inventors.

To be specific, the air duct 411 connected at one end thereof with thefan 41 is connected at the other end thereof with the outlet r1 and r2for sending air to the LCP 34 r. The air duct 421 connected at one endthereof with the fan 42 is connected at the other end thereof with theoutlets g1 and g2 for sending air to the LCP 34 g. The air duct 431connected at one end thereof with the fan 43 is connected at the otherend with the outlet b1 for sending air to the LCP 34 b.

The air duct 411 is preferably configured to deliver a portion of theair sent from the fan 41 to the outlet b2. Furthermore, it is preferableto provide the air duct 431 with a further branching air duct 432 thathas one end connected with the fan 43 and another end having an outletp1 for cooling the PBS.

Next, an overall arrangement of the fans for lowering the internaltemperature of the projector in accordance with the invention will nowbe described in detail.

Arrows in FIG. 18 show directions of air flowing inside and outside theprojector. More particularly, fans 41, 42, and 43 (first, second, andthird fans) inspire cold external air into the projector. The cold airis heated as it cools the optical components such as LCPs, stayingaround the LCPs. However, heat generated by the operating opticalcomponents is much less than that of the lamp. Therefore, thetemperature of the air is still lower than the temperature of the lamp,and the air can be used to cool the lamp. Thus, it is advantageous tocause the fan 16 (fourth fan) to inspire the air lingering around theoptical components such as LCPs and expire the air to the lamp to coolit, as described above. The fan 17 (fifth fan) improves air streams inthe projector so that the air heated by the lamp is discharged out ofthe projector by the fan, thereby lowering the internal temperature ofthe projector.

Referring again to FIG. 18, there is shown an air rectifying plate 500mounted on the inspiration face of the fan 16. The air rectifying plate500 is provided to efficiently guide into the fan 16 the air that hascooled the optical components on the prism and send the air to the lampto cool it.

In the example shown above, a projection type image display apparatus isshown with reference to a projector that utilizes LCPs as light controlelements. It should be understood, however, that the invention can beapplied to image projection type image display apparatuses utilizingother types of image forming optical systems. For example, the inventioncan be applied to a projector utilizing DLP (Digital Light Processing,which is a registered trademark of Texas Instruments (TI), Inc.).

1. A projector having: at least a light source unit; optical componentsadapted to decompose a beam of source light from said light source unitinto beams of three primary colors (red, green, and blue), modulate saidthree colored beams based on an image signal received, compose saidthree modulated beams into a beam of full-color imaging light, andproject said imaging light; and a power supply unit for supplyingelectric power to said light source unit and optical components, saidprojector comprising: a first, second, and third fan each provided nearsaid optical components to introduce external air from outside saidprojector to cool said optical components; a fourth, fifth, and sixthfan for discharging internal air of said projector, and wherein: saidfourth fan adapted to cool said light source unit by blowing into saidlight source unit the air that has been introduced by said first,second, and third fan and cooled said optical components; and said fifthand sixth fans adapted to discharge out of said projector the air thathas cooled said light source unit and said power supply unit.
 2. Theprojector according to claim 1, wherein said first through fourth fansare centrifugal fans.
 3. The projector according to claim 1, whereinsaid fifth and sixth fans are axial fans.
 4. The projector according toclaim 1, wherein said first and third fans are arranged on one side ofsaid optical components, while said second fan is arranged on the otherside of said optical components to face said first and third fans acrosssaid optical components.
 5. The projector according to claim 1, whereinsaid fifth and sixth fans are arranged on one side of said projector andbehind said light source, while said fourth fan is arranged near, and onthe other side of, said light source unit to face said fifth and sixthfans across said light source unit.
 6. The projector according to claim1, wherein the amount of the air to be discharged by each of said fifthand sixth fans is at least 3 times as much as the amount of the airtaken in by each of said first, second, and third fans.
 7. The projectoraccording to claim 1, wherein said fifth fan is adapted to primarilydischarge the air that has cooled said light source unit, while saidsixth fan is adapted to primarily discharge the air that has cooled saidpower supply unit.
 8. The projector according to claim 1, wherein saidfifth and sixth fans are obliquely aligned to each other so that the airstreams expired from these fans cross each other.
 9. The projectoraccording to any one of claims 1 through 8, further comprising arectifying plate for guiding air flow, disposed between said second andfourth fans and near said fourth fan.